UNIQUE PROPERTIES OF A CYTOTOXIC CD4(-CELL LINE ESTABLISHED FROM THE MOUSE INTESTINAL EPITHELIUM()CD8(+) INTRAEPITHELIAL T)

Growth factor-dependent gut intraepithelial lymphocyte (IEL) cell line s were established from a long-term in vitro culture of BALB/c IEL wit h syngeneic irradiated spleen cells in the presence of concanavalin A- stimulated spleen supernatant fluids. The cell lines were preferential ly consisted of very limited thymoindependent subsets of IEL; i.e., Th y-1(+)CD5(-)TCR alpha beta(+)CD4(+)CD8 alpha(+)beta(-) (double-positiv e; DP) IEL and Thy-1(+)CD5(-)TCR alpha beta(+)CD4(-)CD8 alpha(+)beta(- ) (CD8 single-positive; CD8 SP) IEL. The CD8 SP IEL cell line had cyto toxic activities and was triggered to proliferate by T-cell receptor ( TCR)-directed stimuli. The DP IEL cell line expressed high levels of t he CD3-TCR alpha beta, exhibited cytotoxic activity in redirected lysi s assays, and had perforin in the cytoplasm, indicating the functional maturity of this cell line. However, the DP IEL cell line did not pro liferate in response to TCR alpha beta-directed stimuli, which indicat ed that TCR alpha beta-mediated signalling was able to initiate cytoto xic function but not to induce proliferation of the DP IEL cell line. Although both cell lines were shown to have functional competence, the y expressed J11d antigen which marks immaturity in thymocyte different iation pathways. These results indicate that the established thymoinde pendent DP and CD8 SP IEL cell lines have unique properties distinct f rom DP thymocytes and CD8 SP peripheral T cells. Together with a recen t report on freshly isolated DP IEL (10), the unique properties of the DP IEL cell line seems to support the notion that DP IEL may undergo a unique maturation process in the gut microenvironment.